1. Field of the Invention
The present invention is directed to compositions and methods for achieving a stonewashed appearance in fabric while reducing or preventing the backstaining of colorant onto the fabric as well as to the fabric and clothing produced from these methods. In particular, the improved methods of the present invention are directed to contacting the fabrics with an aqueous solution containing a fungal cellulase composition which comprises endoglucanase type components substantially free of CBH type components. When the fabric is treated with such solutions, the amount of backstaining of colorant onto the fabric during the stonewashing of the fabric is reduced.
2. State of the Art
Clothing made from cellulosic fabrics, such as cotton denim, is stiff in texture due to the presence of sizing compositions used to ease manufacturing, handling and assembling of clothing items and typically has a fresh dark dyed appearance. One desirable characteristic of indigo-dyed denim cloth is the alteration of dyed threads with white threads, which gives denim a white on blue appearance.
After a period of extended wear and laundering, the clothing items, particularly denim, can develop in the clothing panels and on seams, localized areas of variation in the form of a lightening, in the depth or density of color. In addition, a general fading of the clothes, some pucker in seams and some wrinkling in the fabric panels can often appear. Additionally, after laundering, sizing is substantially removed from the fabric resulting in a softer feel. In recent years such a distressed or "stonewashed" look, particularly in denim clothing, has become very desirable to a substantial proportion of the public.
The previous methods for producing the distressed look involved stonewashing of a clothing item or items in a large tub with pumice stones having a particle size of about 1 to 10 inches and with smaller pumice particles generated by the abrasive nature of the process. Typically the clothing item is tumbled with the pumice while wet for a sufficient period such that the pumice abrades the fabric to produce in the fabric panels, localized abraded areas of lighter color and similar lightened areas in the seams. Additionally the pumice softens the fabric and produces a fuzzy surface similar to that produced by the extended wear and laundering of the fabric. This method produced the desired white on blue contrast described above.
The use of the pumice stones has several disadvantages, including overload damage to the machine motors, mechanical damage to transport mechanisms and washing drums, environmental waste problems from the grit produced and high labor costs associated with the manual removal of the stones from the pockets of the garments.
In view of the problems associated with pumice stones in stonewashing, whole cellulase solutions are used as a replacement for the pumice stones under agitating and cascading conditions, i.e., in a rotary drum washing machine, to impart a "stonewashed" appearance to the denim (U.S. Pat. No. 4,832,864).
A problem with the use of whole cellulase compositions from Trichoderma sp. microorganisms and other fungal sources is the incomplete removal of colorant caused by redeposition or backstaining of some of the dye back onto the cloth during the stonewashing process. In the case of denim fabric, this causes recoloration of the blue threads and blue coloration of the white threads, resulting in less contrast between the blue and white threads and abrasion points (i.e., a blue on blue look rather than the preferred white on blue). See, American Dyestuff Reporter, Sept. 1990, pp. 24-28. This redeposition is objectionable to some users.
Trichoderma cellulases, even though they result in backstaining are preferred because of their higher activity on denim material. In addition, cellulases with a higher degree of purity may be beneficial in the present invention. High specific activity or a high level of purity results in a higher degree of abrasion in a significantly shorter processing time and therefor, is preferable to the denim processors.
Attempts to reduce the amount of redeposition of dye included the addition of extra chemicals or enzymes, such as surfactants, proteases or other agents, into the cellulase wash to help disperse the loosened dye. In addition, processors have used less active whole cellulase, along with extra washings. However, this results in additional chemical costs and longer processing times. Another method includes the use of a mild bleach agent or stain removing agent in the process. This method affects the garment's final shade and increases the processing time. Finally the use of enzymes and stones together leave the processor with all the problems caused by the use of the stones alone.
Accordingly, it would be desirable to find a method to prevent redeposition of colorant during stonewashing of clothing with cellulases.